I don't have a green thumb and have trouble with
roses that aren't in the ground. But I have heard that some people are successful with them. So I would say it depends on her
plant intuition.
Portulaca are super easy and would love the location.
Celosia would also do well there but they need to be started from
seed because they don't grow once they are transplanted. That is unless you have that green thumb that I don't have.
If you are going to do dwarf fruit
trees my suggestion would be to get two. It would look good from a landscaping standpoint and would help with the polination.